Experimental and theoretical investigation on hydraulic fracturing in cement mortar exposed to sulfate attack

Abstract

To investigate the hydraulic fracturing in sulfate-attacked cement-based materials with tensile stress, splitting tensile strength test, hydraulic fracturing test under splitting load, and scanning electron microscopy test are conducted on cement mortar specimens immersed in Na2SO4 solution. The results reveal that the critical water pressure first increases and then decreases with the increase in immersion time, which is consistent with the tensile strength evolution. The tensile stress promotes the occurrence of hydraulic fracturing. Next, a critical water pressure model is proposed, in which the critical water pressure is expressed as a linear function of tensile strength and nominal tensile stress. Moreover, a theoretical formula is established to reveal the critical water pressure evolution mechanism of cement mortar exposed to sulfate attack. The evolution of critical water pressure depends on the porosity, matrix tensile strength, and expansion stress. Furthermore, a semi-empirical function is proposed to predict the critical water pressure evolution, which exhibits good accuracy. To avoid hydraulic fracturing, decreasing the porosity and tensile stress, increasing the matrix tensile strength, and releasing the expansion stress are effective strategies.